Over the last decade, the prevalence of online learning has dramatically increased. As part of their curriculum, students are expected to spend more and more time watching videos. These videos tend to follow a widespread format: a screen recording of slides with a picture-in-picture (PiP) image of the instructor's face. While this format is ubiquitous, there is mixed evidence that it supports student learning. In this paper, we explore alternative formats for designing educational videos. Based on prior work showing the significance of joint attention for social learning, we create instructional videos augmented with the instructor's gaze and/or face. Testing these formats in a semester-long online course using a 2x2 experimental design, we found that showing the instructor's face had no significant effect on learning, while adding the instructor's eye-tracking data to the video promoted conceptual understanding of the material. Mediation analysis showed that joint visual attention played a significant mediatory role for learning. We conclude by discussing the implications of these findings and formulate recommendations for designing learning videos.